1. 2.1 Atoms, Ions, and Molecules TEKS 3E The student is expected to: 4B investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules and 9A compare the structures and functions of different types of biomolecules, including carbohydrates, lipids, proteins, and nucleic acids

2. 2.1 Atoms, Ions, and Molecules TEKS 3E KEY CONCEPT Living things consist of atoms of different elements

3. 2.1 Atoms, Ions, and Molecules TEKS 3E Living things consist of atoms of different elements. An atom is the smallest basic unit of matter. An element is one type of atom. H O Hydrogen atom (H) Oxygen atom (O)

4. 2.1 Atoms, Ions, and Molecules TEKS 3E –The nucleus has protons and neutrons. –Electrons are in energy levels outside nucleus. Oxygen atom (O) Nucleus: 8 protons (+) 8 neutrons outermost energy level: 6 electrons (-) inner energy level: 2 electrons (-) An atom has a nucleus and electrons.

5. 2.1 Atoms, Ions, and Molecules TEKS 3E –Protons with a positive charge –Electrons with a negative charge –Neutrons with a neutral charge/ no charge

6. Elements  Elements are pure substances made up of one kind of atom.  All atoms of that element look just the same, with the same number of protons, neutrons (average), and electrons.  The number of protons indicates the type of atom.

7. 2.1 Atoms, Ions, and Molecules TEKS 3E –water (H 2 O) O HH _ ++ A compound is made of atoms of different elements bonded together.

8. 2.1 Atoms, Ions, and Molecules TEKS 3E –carbon dioxide (CO 2 ) A compound is made of atoms of different elements bonded together. –water (H 2 O)

9. 2.1 Atoms, Ions, and Molecules TEKS 3E –many other carbon-based compounds in living things A compound is made of atoms of different elements bonded together. –water (H 2 O) –carbon dioxide (CO 2 )

10. 2.1 Atoms, Ions, and Molecules TEKS 3E Ions form when atoms gain or lose electrons. An ion is an atom that has gained or lost one or more electrons. –positive ions form when atoms lose electrons –negative ions form when atoms gain electrons Ionic bonds form between oppositely charged ions. Sodium atom (Na)Chlorine atom (CI)Sodium ion (Na + )Chloride ion (CI - ) Na loses an electron to CI ionic bond gained electron

11. 2.1 Atoms, Ions, and Molecules TEKS 3E Atoms share pairs of electrons in covalent bonds. A covalent bond forms when atoms share a pair of electrons. covalent bonds Oxygen atom (O)Carbon atom (C)Oxygen atom (O) Carbon dioxide (CO 2 ) –multiple covalent bonds –diatomic molecules

12. 2.1 Atoms, Ions, and Molecules TEKS 3E Isotopes are uncharged atoms with a different atomic mass than the common element. Count the number of neutrons in each isotope of carbon above

13. 2.1 Atoms, Ions, and Molecules TEKS 3E Isotopes Carbon-12 Carbon-14 P = 6P = 6 N = 6N = 8 e = 6e = 6 Carbon-14 has two more neutrons than Carbon-12. it’s nucleus has a greater mass.

14. 2.1 Atoms, Ions, and Molecules TEKS 3E Some isotopes are radioactive and break down at a constant rate over time. We can use these to help date rocks and fossils, use them to treat cancers, and use them as biological markers within an organism

15. 2.1 Atoms, Ions, and Molecules TEKS 3E The student is expected to: 4B investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules and 9A compare the structures and functions of different types of biomolecules, including carbohydrates, lipids, proteins, and nucleic acids

16. 2.1 Atoms, Ions, and Molecules TEKS 3E O HH _ ++ Life depends on hydrogen bonds in water. Water is a polar molecule. –Polar molecules have slightly charged regions. – Nonpolar molecules do not have charged regions. – Hydrogen bonds form between slightly positive hydrogen atoms and slightly negative atoms.

17. Although water is an electrically neutral molecule it is does exhibit polarity. Polarity refers to the unequal sharing of electrons. Polarity creates partial positive charges and partial negative charges on each water molecule. The electrons spend more time around oxygen than they do around Hydrogen. Hydrogen is NAKED!

18. POLARITY The shared electrons between oxygen and hydrogen tend to spend more time orbiting the oxygen atom giving it a unequal charge distribution e In a water molecule, are the electrons more likely to be near the oxygen nucleus or the hydrogen nucleus? _______________ Oxygen nucleus

19. The oxygen end gets a partial negative charge Hydrogen end gets a partial positive charge

20. Negative charges are attracted to positive charges. In a water molecule the negative oxygen end is attracted to the positive hydrogen end of another molecule This creates a weak Hydrogen Bond between water molecules

21. Hydrogen bonding H H H H H H H H H H H H O O O O O O (-) (+) the charges in parentheses are partial charges Water can form multiple hydrogen bonds between molecules

22. 2.2 Properties of Water TEKS 4B, 9A Hydrogen bonds are responsible for some important properties of water. –high specific heat –Cohesion a)Surface tension –Adhesion b)meniscus

23. Cohesion Cohesion is an attraction between molecules of the same substance. Water is very cohesive because of hydrogen bonding.

24. Cohesion creates surface tension The weight of the paper clip isn’t enough to break the weak hydrogen bonds between the water molecules A measure of how difficult it is to stretch or break the surface of a liquid.

25. Water striders rely on cohesion between water molecules

26. Adhesion Adhesion is an attraction between molecules of different substances. Water also sticks to, or adheres, to other surfaces well. This is why a meniscus forms when you are measuring liquid.

27. Capillary action Cohesion and adhesion combined allows water to move up certain materials. This is how plants get water from the ground up through their stems

28. Polarity also affects Solubility Solubility refers to the ability of one substance (solute) to dissolve in another (solvent)

29. 2.2 Properties of Water TEKS 4B, 9A Many compounds dissolve in water. A solution is formed when one substance dissolves in another. – A solution is a homogeneous mixture. – Solvents dissolve other substances. – Solutes dissolve in a solvent. solution

30. Solubility Polar substances can dissolve other polar substances. Non-polar substances dissolve other non- polar substances. Polar substances and non-polar substances do not mix.

31. 2.2 Properties of Water TEKS 4B, 9A “Like dissolves like.” –Polar solvents dissolve polar solutes. –Nonpolar solvents dissolve nonpolar solutes. –Polar substances and nonpolar substances generally remain separate.

32. Water is a polar molecule Oil is a non-polar molecule Oil and water do not mix for this reason

33. 2.2 Properties of Water TEKS 4B, 9A Some compounds form acids or bases. An acid releases a hydrogen ion when it dissolves in water. – high H + concentration – pH less than 7 more acidic stomach acid pH between 1 and 3

34. 2.2 Properties of Water TEKS 4B, 9A A base removes hydrogen ions from a solution. –low H + concentration –pH greater than 7 bile pH between 8 and 9 more basic

35. 2.2 Properties of Water TEKS 4B, 9A A neutral solution has a pH of 7. pure water pH 7

36. Myth: All acids are harmful and will burn your skin. Busted: Not all acids cause burns…some examples are lemon juice and vinegar

37. Myth: Bases are safe to handle Busted: Lye or Sodium Hydroxide is very dangerous